TARARIUM Aquarium Filter U-V for 20-75 Gallon, 200GPH Fish Tank Filter w/ 5W U-V Light Green Clean Machine Submersible Powerful Pump Internal Filter for Turtle Tank Saltwater Freshwater Crystal ClearCRYSTAL CLEAR Turns CLOUDY and GREEN water crystal clear in 3 7 days. The larger the fish tank, the longer it takes. Reduce the number of water changes in the fish tank. DOUBLE FILTRATION First stage Biochemical Sponge Filter. Second stage 254nm wavelength U V Light. SEPARATE SWITCHES Control the water pump and fish tank light separately. When you only want to use the aquarium filter function, you can turn off the fish tank U V light separately.